Tin (50Sn) is the element with the greatest number of stable isotopes (ten; three of them are potentially radioactive but have not been observed to decay), which is probably related to the fact that 50 is a "magic number" of protons. 29 additional unstable isotopes are known, including the "doubly magic" tin-100 (100Sn) (discovered in 1994)[2] and tin-132 (132Sn). The longest-lived radioisotope is 126Sn, with a half-life of 230,000 years. The other 28 radioisotopes have half-lives less than a year.

Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.

Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.

Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.

1.
Isotope
–
Isotopes are variants of a particular chemical element which differ in neutron number. All isotopes of an element have the same number of protons in each atom. The number of protons within the nucleus is called atomic number and is equal to the number of electrons in the neutral atom. Each atomic number identifies a specific element, but not the isotope, the number of nucleons in the nucleus is the atoms mass number, and each isotope of a given element has a different mass number. For example, carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon with mass numbers 12,13 and 14 respectively. The atomic number of carbon is 6, which means that carbon atom has 6 protons. Nuclide refers to a rather than to an atom. Identical nuclei belong to one nuclide, for each nucleus of the carbon-13 nuclide is composed of 6 protons and 7 neutrons. The nuclide concept emphasizes nuclear properties over chemical properties, whereas the isotope concept emphasizes chemical over nuclear, the neutron number has large effects on nuclear properties, but its effect on chemical properties is negligible for most elements. Because isotope is the term, it is better known than nuclide. An isotope and/or nuclide is specified by the name of the particular element followed by a hyphen, when a chemical symbol is used, e. g. C for carbon, standard notation is to indicate the number with a superscript at the upper left of the chemical symbol. Because the atomic number is given by the element symbol, it is common to only the mass number in the superscript. The letter m is sometimes appended after the number to indicate a nuclear isomer. For example, 14C is a form of carbon, whereas 12C. There are about 339 naturally occurring nuclides on Earth, of which 286 are primordial nuclides, primordial nuclides include 32 nuclides with very long half-lives and 254 that are formally considered as stable nuclides, because they have not been observed to decay. In most cases, for reasons, if an element has stable isotopes. Theory predicts that many apparently stable isotopes/nuclides are radioactive, with extremely long half-lives, of the 254 nuclides never observed to decay, only 90 of these are theoretically stable to all known forms of decay

2.
Radioactive decay
–
A material containing such unstable nuclei is considered radioactive. Certain highly excited short-lived nuclear states can decay through neutron emission, or more rarely, however, for a collection of atoms, the collections expected decay rate is characterized in terms of their measured decay constants or half-lives. This is the basis of radiometric dating, the half-lives of radioactive atoms have no known upper limit, spanning a time range of over 55 orders of magnitude, from nearly instantaneous to far longer than the age of the universe. A radioactive nucleus with spin can have no defined orientation. If there are multiple particles produced during a single decay, as in decay, their relative angular distribution. Such a parent process could be a previous decay, or a nuclear reaction, the decaying nucleus is called the parent radionuclide, and the process produces at least one daughter nuclide. Except for gamma decay or internal conversion from an excited state. When the number of changes, an atom of a different chemical element is created. The first decay processes to be discovered were alpha decay, beta decay, alpha decay occurs when the nucleus ejects an alpha particle. This is the most common process of emitting nucleons, but highly excited nuclei can eject single nucleons, or in the case of cluster decay, specific light nuclei of other elements. Beta decay occurs when the nucleus emits an electron or positron, the nucleus may capture an orbiting electron, causing a proton to convert into a neutron in a process called electron capture. All of these result in a well-defined nuclear transmutation. By contrast, there are radioactive decay processes that do not result in a nuclear transmutation, another type of radioactive decay results in products that vary, appearing as two or more fragments of the original nucleus with a range of possible masses. For a summary table showing the number of stable and radioactive nuclides in each category, there are 29 naturally occurring chemical elements on Earth that are radioactive. They are those that contain 34 radionuclides that date before the time of formation of the solar system, well-known examples are uranium and thorium, but also included are naturally occurring long-lived radioisotopes, such as potassium-40. Radioactivity was discovered in 1896 by the French scientist Henri Becquerel and these materials glow in the dark after exposure to light, and he suspected that the glow produced in cathode ray tubes by X-rays might be associated with phosphorescence. He wrapped a photographic plate in black paper and placed various phosphorescent salts on it, all results were negative until he used uranium salts. The uranium salts caused a blackening of the plate in spite of the plate being wrapped in black paper and these radiations were given the name Becquerel Rays

3.
Natural abundance
–
In physics, natural abundance refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass of these isotopes is the weight listed for the element in the periodic table. The abundance of an isotope varies from planet to planet, and even place to place on the Earth. As an example, uranium has three naturally occurring isotopes, 238U, 235U and 234U and their respective natural mole-fraction abundances are 99. 2739–99. 2752%,0. 7198–0. 7202%, and 0. 0050–0. 0059%. For example, if 100,000 uranium atoms were analyzed, one would expect to find approximately 99,274 238U atoms, approximately 720 235U atoms, and very few 234U atoms. This is because 238U is much more stable than 235U or 234U, exactly because the different uranium isotopes have different half-lives, when the Earth was younger, the isotopic composition of uranium was different. As an example,1.7 billion years ago the NA of 235U was 3. 1% compared with todays 0. 7% and it is now known from study of the sun and primitive meteorites that the solar system was initially almost homogeneous in isotopic composition. There is also evidence for injection of short-lived isotopes from a supernova explosion that may have triggered solar nebula collapse. Hence deviations from natural abundance on earth are often measured in parts per thousand because they are less than one percent, the single exception to this lies with the presolar grains found in primitive meteorites. These bypassed the homogenization, and often carry the signature of specific nucleosynthesis processes in which their elements were made. In these materials, deviations from natural abundance are sometimes measured in factors of 100, the next table gives the isotope distributions for some elements. Some elements like phosphorus and fluorine only exist as a single isotope, berkeley Isotopes Project Interactive Table Scientific Instrument Services List Tools to compute low and high precision isotopic distribution

4.
Half-life
–
Half-life is the time required for a quantity to reduce to half its initial value. The term is used in nuclear physics to describe how quickly unstable atoms undergo. The term is used more generally to characterize any type of exponential or non-exponential decay. For example, the medical sciences refer to the biological half-life of drugs, the converse of half-life is doubling time. The original term, half-life period, dating to Ernest Rutherfords discovery of the principle in 1907, was shortened to half-life in the early 1950s. Rutherford applied the principle of a radioactive elements half-life to studies of age determination of rocks by measuring the period of radium to lead-206. Half-life is constant over the lifetime of an exponentially decaying quantity, the accompanying table shows the reduction of a quantity as a function of the number of half-lives elapsed. A half-life usually describes the decay of discrete entities, such as radioactive atoms, in that case, it does not work to use the definition that states half-life is the time required for exactly half of the entities to decay. For example, if there are 3 radioactive atoms with a half-life of one second, instead, the half-life is defined in terms of probability, Half-life is the time required for exactly half of the entities to decay on average. In other words, the probability of a radioactive atom decaying within its half-life is 50%, for example, the image on the right is a simulation of many identical atoms undergoing radioactive decay. Note that after one half-life there are not exactly one-half of the remaining, only approximately. Nevertheless, when there are many identical atoms decaying, the law of large numbers suggests that it is a good approximation to say that half of the atoms remain after one half-life. There are various simple exercises that demonstrate probabilistic decay, for example involving flipping coins or running a computer program. The three parameters t1⁄2, τ, and λ are all related in the following way. Amount approaches zero as t approaches infinity as expected, some quantities decay by two exponential-decay processes simultaneously. There is a half-life describing any exponential-decay process, for example, The current flowing through an RC circuit or RL circuit decays with a half-life of RCln or lnL/R, respectively. For this example, the half time might be used instead of half life. In a first-order chemical reaction, the half-life of the reactant is ln/λ, in radioactive decay, the half-life is the length of time after which there is a 50% chance that an atom will have undergone nuclear decay

5.
Decay product
–
In nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps, 234Th is the daughter of the parent 238U. 234mPa is the granddaughter of 238U and these might also be referred to as the daughter products of 238U. Decay products are important in understanding radioactive decay and the management of radioactive waste, for elements above lead in atomic number, the decay chain typically ends with an isotope of thallium or lead. In many cases members of the chain are far more radioactive than the original nuclide. Thus, although uranium is not dangerously radioactive when pure, some pieces of naturally occurring pitchblende are quite dangerous owing to their radium content, similarly, thorium gas mantles are very slightly radioactive when new, but become far more radioactive after only a few months of storage. Although it cannot be predicted whether any given atom of a substance will decay at any given time. Because of this, decay products are important to scientists in many fields who need to know the quantity or type of the parent product, such studies are done to measure pollution levels and for other matters

6.
Stable isotope
–
The term stable isotope has a similar meaning to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element, the relative abundance of such stable isotopes can be measured experimentally, yielding an isotope ratio that can be used as a research tool. Theoretically, such stable isotopes could include the radiogenic daughter products of radioactive decay, however, the expression stable isotope ratio is preferably used to refer to isotopes whose relative abundances are affected by isotope fractionation in nature. This field is termed stable isotope geochemistry, measurement of the ratios of naturally occurring stable isotopes plays an important role in isotope geochemistry, but stable isotopes are also finding uses in ecological and biological studies. Other workers have used oxygen isotope ratios to reconstruct historical atmospheric temperatures, the long history of study of these elements is in part because the proportions of stable isotopes in these light and volatile elements is relatively easy to measure. However, recent advances in isotope ratio mass spectrometry now enable the measurement of isotope ratios in heavier elements, such as iron, copper, zinc, molybdenum. The variations in oxygen and hydrogen isotope ratios have applications in hydrology since most samples will lie between two extremes, ocean water and Arctic/Antarctic snow, stable isotopes of water are also used in partitioning water sources for plant transpiration and groundwater recharge. Another application is in paleotemperature measurement for paleoclimatology, for example, one technique is based on the variation in isotopic fractionation of oxygen by biological systems with temperature. Species of Foraminifera incorporate oxygen as calcium carbonate in their shells, the ratio of the oxygen isotopes oxygen-16 and oxygen-18 incorporated into the calcium carbonate varies with temperature and the oxygen isotopic composition of the water. This oxygen remains fixed in the calcium carbonate when the dies, falls to the sea bed. In forensic science, research suggests that the variation in certain isotope ratios in drugs derived from plant sources can be used to determine the drugs continent of origin and it also has applications in doping control, to distinguish between endogenous and exogenous sources of hormones. Chondrite meteorites are classified using the isotope ratios. In addition, a signature of carbon-13 confirms the non-terrestrial origin for organic compounds found in carbonaceous chondrites

7.
Beta emission
–
In nuclear physics, beta decay is a type of radioactive decay in which a beta ray, and a neutrino are emitted from an atomic nucleus. Neither the beta particle nor its associated neutrino exist within the prior to beta decay. By this process, unstable atoms obtain a more stable ratio of protons to neutrons, the probability of a nuclide decaying due to beta and other forms of decay is determined by its binding energy. The binding energies of all existing nuclides form what is called the valley of stability. Beta decay is a consequence of the force, which is characterized by relatively lengthy decay times. Nucleons are composed of up or down quarks, and the force allows a quark to change type by the exchange of a W boson. For example, a neutron, composed of two quarks and an up quark, decays to a proton composed of a down quark. Decay times for many nuclides that are subject to beta decay can be thousands of years, electron capture is sometimes included as a type of beta decay, because the basic nuclear process, mediated by the weak force, is the same. In electron capture, an atomic electron is captured by a proton in the nucleus, transforming it into a neutron. The two types of decay are known as beta minus and beta plus. β+ decay is known as positron emission. Beta decay conserves a number known as the lepton number, or the number of electrons. These particles have lepton number +1, while their antiparticles have lepton number −1, since a proton or neutron has lepton number zero, β+ decay must be accompanied with an electron neutrino, while β− decay must be accompanied by an electron antineutrino. This new element has a mass number A, but an atomic number Z that is increased by one. As in all nuclear decays, the element is known as the parent nuclide while the resulting element is known as the daughter nuclide. The beta spectrum, or distribution of values for the beta particles, is continuous. The total energy of the process is divided between the electron, the antineutrino, and the recoiling nuclide. In the figure to the right, an example of an electron with 0.40 MeV energy from the decay of 210Bi is shown

8.
Standard atomic weight
–
The standard atomic weight is a physical quantity for a chemical element, expressed as relative atomic mass. It is specified by the IUPAC definition of natural, stable, because of this practical definition, the value is widely used as the atomic weight for real life substances. For example, in pharmaceuticals and scientific research, out of 118 chemical elements,84 are stable and have this Earth-environment based value. Typically, such a value is, for example helium, Ar, the indicates the uncertainty in the last digit shown, or 4.002602 ±0.000002. For twelve elements various terrestial sources diverge on this value, because these sources have a different decay history, for example, thallium in sedimentary rocks has a different isotopic composition than when in igneous rocks and volcanic gases. For these elements, the atomic weight is noted as an interval, Ar. CIAAW also publishes abridged values, and simple conventional values for interval values, the standard atomic weight is a more specific value of a relative atomic mass. It is defined as the atomic mass of a source in the local environment of the Earths crust and atmosphere as determined by the IUPAC Commission on Atomic Weights. In general, values from different sources are subject to variation due to a different radioactive history of sources. By limiting the sources to terrestial origin only, the CIAAW determined values have less variance, the CIAAW-published values are used and sometimes lawfully required in mass calculations. The values have an uncertainty, or are an expectation interval and this uncertainty reflects natural variability in isotopic distribution for an element, rather than uncertainty in measurement. For synthetic elements the isotope formed depends on the means of synthesis, therefore, for synthetic elements the total nucleon count of the most stable isotope is listed in brackets, in place of the standard atomic weight. When the term weight is used in chemistry, usually it is the more specific standard atomic weight that is implied. It is standard atomic weights that are used in periodic tables, the abridged atomic weight, also published by CIAAW, is derived from the standard atomic weight reducing the numbers to five digits. The name does not say rounded, interval borders are rounded downwards for the first border, and upwards for th upward border. This way, the precise original interval is fully covered. For example, hydrogen has Ar, standard = and this notation states that the various sources on Earth have substantially different isotopic constitutions, and uncertainties are incorporated in the two numbers. For these elements, there is not an Earth average constitution, however, for situations where a less precise value is acceptable, CIAAW has published a single-number conventional atomic weight that can be used for example in trade

9.
Tin
–
Tin is a chemical element with symbol Sn and atomic number 50. It is a metal in group 14 of the periodic table. It is obtained chiefly from the mineral cassiterite, which contains tin dioxide, Tin shows a chemical similarity to both of its neighbors in group 14, germanium and lead, and has two main oxidation states, +2 and the slightly more stable +4. Tin is the 49th most abundant element and has, with 10 stable isotopes, metallic tin is not easily oxidized in air. The first alloy used on a scale was bronze, made of tin and copper. After 600 BC, pure metallic tin was produced, pewter, which is an alloy of 85–90% tin with the remainder commonly consisting of copper, antimony, and lead, was used for flatware from the Bronze Age until the 20th century. In modern times, tin is used in alloys, most notably tin/lead soft solders. Another large application for tin is corrosion-resistant tin plating of steel, inorganic tin compounds are rather non-toxic. Because of its low toxicity, tin-plated metal was used for packaging as tin cans. However, overexposure to tin may cause problems with metabolizing essential trace elements such as copper and zinc, Tin is a soft, malleable, ductile and highly crystalline silvery-white metal. When a bar of tin is bent, a sound known as the tin cry can be heard from the twinning of the crystals. Tin melts at the low temperature of about 232 °C, the lowest in group 14, the melting point is further lowered to 177.3 °C for 11 nm particles. β-tin, which is stable at and above room temperature, is malleable, in contrast, α-tin, which is stable below 13.2 °C, is brittle. α-tin has a cubic crystal structure, similar to diamond. α-tin has no properties at all because its atoms form a covalent structure in which electrons cannot move freely. It is a dull-gray powdery material with no common uses other than a few specialized semiconductor applications and these two allotropes, α-tin and β-tin, are more commonly known as gray tin and white tin, respectively. Two more allotropes, γ and σ, exist at temperatures above 161 °C, in cold conditions, β-tin tends to transform spontaneously into α-tin, a phenomenon known as tin pest. Commercial grades of tin resist transformation because of the effect of the small amounts of bismuth, antimony, lead

10.
List of elements by stability of isotopes
–
This is a list of the chemical elements and their isotopes, listed in terms of stability. Atomic nuclei consist of protons and neutrons, which each other through the nuclear force. These two forces compete, leading to some combinations of neutrons and protons being more stable than others, neutrons stabilize the nucleus, because they attract protons, which helps offset the electrical repulsion between protons. Unstable isotopes decay through various radioactive decay pathways, most commonly alpha decay, beta decay, many other rare types of decay, such as spontaneous fission or cluster decay are known. Of the first 82 elements in the table,80 have isotopes considered to be stable. Technetium, promethium and all the elements with a number over 82 only have isotopes that are known to decompose through radioactive decay. No undiscovered elements are expected to be stable, therefore lead is considered the heaviest stable element, however, it is possible that some isotopes that are now considered stable will be revealed to decay with extremely long half-lives. This list depicts what is agreed upon by the consensus of the community as of 2008. For each of the 80 stable elements, the number of the isotopes is given. Only 90 isotopes are expected to be stable, and an additional 164 are energetically unstable. Thus,254 isotopes are stable by definition and those that may in the future be found to be radioactive, are expected to have half-lives longer than 1022 years. Additionally, about 29 nuclides of the naturally occurring elements have isotopes with a half-life larger than the age of the Solar System. An additional six nuclides have half-lives longer than 100 million years, which is far less than the age of the solar system and these 32 radioactive naturally occurring nuclides comprise the radioactive primordial nuclides. The total number of nuclides is then 254 plus the 32 radioactive primordial nuclides. This number is subject to change if new shorter-lived primordials are identified on Earth, one of the primordial nuclides is Ta-180m, which is predicted to have a half-life in excess of 1015 years, but has never been observed to decay. Another notable example is the naturally occurring isotope of bismuth, which has been predicted to be unstable with a very long half-life. Because of their long half-lives, such isotopes are found on Earth in various quantities. All the primordial isotopes are given in order of their abundance on Earth

11.
Magic number (physics)
–
In nuclear physics, a magic number is a number of nucleons such that they are arranged into complete shells within the atomic nucleus. The seven most widely recognized magic numbers as of 2007 are 2,8,20,28,50,82, large isotopes with magic numbers of nucleons are said to exist in an island of stability. Unlike the magic numbers 2–126, which are realized in spherical nuclei, before this was realized, higher magic numbers, such as 184,258,350, and 462, were predicted based on simple calculations that assumed spherical shapes, these are generated by the formula 2. It is now believed that the sequence of spherical magic numbers cannot be extended in this way, further predicted magic numbers are 114,122,124, and 164 for protons as well as 184,196,236, and 318 for neutrons. It seemed a little magic to him, and that is how the words ‘Magic Numbers’ were coined. ”Nuclei which have neutron number and proton numbers each equal to one of the magic numbers are called double magic. Examples of double magic isotopes include helium-4, oxygen-16, calcium-40, calcium-48, nickel-48, nickel-78, double-magic effects may allow existence of stable isotopes which otherwise would not have been expected. An example is calcium-40, with 20 neutrons and 20 protons, both calcium-48 and nickel-48 are double magic because calcium-48 has 20 protons and 28 neutrons while nickel-48 has 28 protons and 20 neutrons. Calcium-48 is very neutron-rich for such an element, but like calcium-40. Nickel-48, discovered in 1999, is the most proton-rich isotope known beyond helium-3, at the other extreme, nickel-78 is also doubly magical, with 28 protons and 50 neutrons, a ratio observed only in much heavier elements apart from tritium with one proton and two neutrons. Magic number shell effects are seen in ordinary abundances of elements, helium-4 is among the most abundant nuclei in the universe, Magic effects can keep unstable nuclides from decaying as rapidly as would otherwise be expected. For example, the nuclides tin-100 and tin-132 are examples of doubly magic isotopes of tin that are unstable, and represent endpoints beyond which stability drops off rapidly. In December 2006 hassium-270, with 108 protons and 162 neutrons, was discovered by a team of scientists led by the Technical University of Munich having the half-life of 22 seconds. Hassium-270 evidently forms part of an island of stability, and may even be double magic, Nuclear shells are said to occur when the separation between energy levels is significantly greater than the local mean separation. In the shell model for the nucleus, magic numbers are the numbers of nucleons at which a shell is filled. For instance the magic number 8 occurs when 1s1/2, 1p3/2, 1p1/2 energy levels are filled as there is an energy gap between the 1p1/2 and the next highest 1d5/2 energy levels. The atomic analog to nuclear magic numbers are numbers of electrons leading to discontinuities in the ionization energy. These occur for the noble gases helium, neon, argon, krypton, xenon, radon and oganesson, hence, the atomic magic numbers are 2,10,18,36,54,86 and 118. In 2007, Jozsef Garai from Florida International University proposed a formula describing the periodicity of the nucleus in the periodic system based on the double tetrahedron

12.
Fission product yield
–
Nuclear fission splits a heavy nucleus such as uranium or plutonium into two lighter nuclei, which are called fission products. Yield refers to the fraction of a product produced per fission. Yield can be broken down by, Individual isotope Chemical element spanning several isotopes of different mass number, nuclei of a given mass number regardless of atomic number. Known as chain yield because it represents a decay chain of beta decay, a few isotopes can be produced directly by fission, but not by beta decay because the would-be precursor with atomic number one greater is stable and does not decay. Chain yields do not account for these isotopes, however. Yield is usually stated as percentage per fission, so that the total yield percentages sum to 200%, less often, it is stated as percentage of all fission products, so that the percentages sum to 100%. Ternary fission, about 0. 2% to 0. 4% of fissions and this is because the fission event causes the nucleus to split in an asymmetric manner, as nuclei closer to magic numbers are more stable. Yield vs. Z - This is a distribution for the fission of uranium. Note that in the used to make this graph the activation of fission products was ignored. In this bar chart results are shown for different cooling times, because of the stability of nuclei with even numbers of protons and/or neutrons the curve of yield against element is not a smooth curve. The curves for the fission of the later actinides tend to even more shallow valleys. In extreme cases such as 259Fm, only one peak is seen, yield is usually expressed relative to number of fissioning nuclei, not the number of fission product nuclei, that is, yields should sum to 200%. The table in the next section gives yields for notable radioactive fission products, and neutron poison fission products, from thermal neutron fission of U-235, computed from

13.
Nuclear waste
–
Radioactive waste is waste that contains radioactive material. Radioactive waste is usually a by-product of nuclear generation and other applications of nuclear fission or nuclear technology, such as research. Radioactive waste is hazardous to most forms of life and the environment, and is regulated by government agencies in order to protect human health and the environment. Radioactivity naturally decays over time, so radioactive waste has to be isolated and confined in appropriate facilities for a sufficient period until it no longer poses a threat. The time radioactive waste must be stored for depends on the type of waste, Radioactive waste typically comprises a number of radionuclides, unstable configurations of elements that decay, emitting ionizing radiation which can be harmful to humans and the environment. These isotopes emit different types and levels of radiation, which last for different periods of time, the radioactivity of all radioactive waste diminishes with time. Certain radioactive elements will remain hazardous to humans and other creatures for hundreds or thousands of years, other radionuclides remain radioactive for millions of years. Thus, these wastes must be shielded for centuries and isolated from the environment for millennia. Since radioactive decay follows the rule, the rate of decay is inversely proportional to the duration of decay. In other words, the radiation from a long-lived isotope like iodine-129 will be less intense than that of a short-lived isotope like iodine-131. The two tables show some of the radioisotopes, their half-lives, and their radiation yield as a proportion of the yield of fission of uranium-235. The energy and the type of the radiation emitted by a radioactive substance are also important factors in determining its threat to humans. The chemical properties of the element will determine how mobile the substance is and how likely it is to spread into the environment. Exposure to radioactive waste may cause harm or death. In humans, a dose of 1 sievert carries a 5. 5% risk of developing cancer, ionizing radiation causes deletions in chromosomes. If a developing organism such as a child is irradiated, it is possible a birth defect may be induced. The incidence of radiation-induced mutations in humans is small, as in most mammals, because of natural cellular-repair mechanisms, Radioactive waste comes from a number of sources. Waste from the front end of the fuel cycle is usually alpha-emitting waste from the extraction of uranium

14.
Actinides
–
The actinide /ˈæktᵻnaɪd/ or actinoid /ˈæktᵻnɔɪd/ series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, the informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide. All but one of the actinides are f-block elements, corresponding to the filling of the 5f electron shell, lawrencium, in comparison with the lanthanides, also mostly f-block elements, the actinides show much more variable valence. They all have very large atomic and ionic radii and exhibit a large range of physical properties. While actinium and the late actinides behave similarly to the lanthanides, all actinides are radioactive and release energy upon radioactive decay, naturally occurring uranium and thorium, and synthetically produced plutonium are the most abundant actinides on Earth. These are used in nuclear reactors and nuclear weapons, uranium and thorium also have diverse current or historical uses, and americium is used in the ionization chambers of most modern smoke detectors. Of the actinides, primordial thorium and uranium occur naturally in substantial quantities, the radioactive decay of uranium produces transient amounts of actinium and protactinium, and atoms of neptunium and plutonium are occasionally produced from transmutation reactions in uranium ores. The other actinides are purely synthetic elements, like the lanthanides, the actinides form a family of elements with similar properties. Within the actinides, there are two overlapping groups, transuranium elements, which follow uranium in the periodic table—and transplutonium elements, compared to the lanthanides, which are found in nature in appreciable quantities, most actinides are rare. The most abundant, or easily synthesized actinides are uranium and thorium, the existence of transuranium elements was suggested by Enrico Fermi based on his experiments in 1934. However, even though four actinides were known by that time, synthesis of transuranics gradually undermined this point of view. By 1944 an observation that curium failed to exhibit oxidation states above 4 prompted Glenn Seaborg to formulate a so-called actinide hypothesis, at present, there are two major methods of producing isotopes of transplutonium elements, irradiation of the lighter elements with either neutrons or accelerated charged particles. The advantage of the method is that elements heavier than plutonium, as well as neutron-deficient isotopes, can be obtained. In 1962–1966, there were attempts in the United States to produce transplutonium isotopes using a series of six underground nuclear explosions and this inobservation was attributed to spontaneous fission owing to the large speed of the products and to other decay channels, such as neutron emission and nuclear fission. Uranium and thorium were the first actinides discovered, uranium was identified in 1789 by the German chemist Martin Heinrich Klaproth in pitchblende ore. He named it after the planet Uranus, which had been discovered eight years earlier. Klaproth was able to precipitate a yellow compound by dissolving pitchblende in nitric acid and he then reduced the obtained yellow powder with charcoal, and extracted a black substance that he mistook for metal. Only 60 years later, the French scientist Eugène-Melchior Péligot identified it with uranium oxide and he also isolated the first sample of uranium metal by heating uranium tetrachloride with potassium

15.
Nuclear fission
–
In nuclear physics and nuclear chemistry, nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts. The fission process often produces free neutrons and gamma photons, Frisch named the process by analogy with biological fission of living cells. It is a reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments. In order for fission to produce energy, the binding energy of the resulting elements must be less negative than that of the starting element. Fission is a form of nuclear transmutation because the fragments are not the same element as the original atom. The two nuclei produced are most often of comparable but slightly different sizes, typically with a ratio of products of about 3 to 2. Most fissions are binary fissions, but occasionally, three positively charged fragments are produced, in a ternary fission, the smallest of these fragments in ternary processes ranges in size from a proton to an argon nucleus. Nuclear fission produces energy for power and drives the explosion of nuclear weapons. Both uses are possible because certain substances called nuclear fuels undergo fission when struck by fission neutrons and this makes possible a self-sustaining nuclear chain reaction that releases energy at a controlled rate in a nuclear reactor or at a very rapid uncontrolled rate in a nuclear weapon. Nuclear fission can occur without neutron bombardment as a type of radioactive decay and this type of fission is rare except in a few heavy isotopes. In engineered nuclear devices, essentially all nuclear fission occurs as a nuclear reaction — a bombardment-driven process that results from the collision of two subatomic particles, in nuclear reactions, a subatomic particle collides with an atomic nucleus and causes changes to it. Nuclear reactions are driven by the mechanics of bombardment, not by the relatively constant exponential decay. Many types of reactions are currently known. Nuclear fission differs importantly from other types of reactions, in that it can be amplified. In such a reaction, free neutrons released by each fission event can trigger yet more events, the chemical element isotopes that can sustain a fission chain reaction are called nuclear fuels, and are said to be fissile. The most common nuclear fuels are 235U and 239Pu and these fuels break apart into a bimodal range of chemical elements with atomic masses centering near 95 and 135 u. Most nuclear fuels undergo spontaneous fission only very slowly, decaying instead mainly via an alpha-beta decay chain over periods of millennia to eons. In a nuclear reactor or nuclear weapon, the majority of fission events are induced by bombardment with another particle, a neutron

16.
Thermal neutron
–
The neutron detection temperature, also called the neutron energy, indicates a free neutrons kinetic energy, usually given in electron volts. The term temperature is used, since hot, thermal and cold neutrons are moderated in a medium with a certain temperature, the neutron energy distribution is then adopted to the Maxwellian distribution known for thermal motion. Qualitatively, the higher the temperature, the higher the energy of the free neutrons. Kinetic energy, speed and wavelength of the neutron are related through the De Broglie relation, but different ranges with different names are observed in other sources. After a number of collisions with nuclei in a medium at this temperature, neutrons arrive at about this energy level, Neutrons of energy greater than thermal Greater than 0.2 eV Neutrons which are strongly absorbed by cadmium Less than 0.4 eV. Neutrons which are not strongly absorbed by cadmium Greater than 0.6 eV, Neutrons of energy slightly greater than epicadmium neutrons. Refers to neutrons which are strongly susceptible non-fission capture by U-238,1 eV to 300 eV Neutrons that are between slow and fast Few hundred eV to 0.5 MeV. A fast neutron is a neutron with a kinetic energy level close to 1 MeV, hence a speed of 14,000 km/s. They are named fast neutrons to distinguish them from lower-energy thermal neutrons, fast neutrons are produced by nuclear processes, nuclear fission produces neutrons with a mean energy of 2 MeV, which qualifies as fast. Spontaneous fission is a type of decay that some heavy elements undergo. Nuclear fusion, deuterium–tritium fusion produces neutrons of 14.1 MeV that can easily fission uranium-238, neutron emission occurs in very rare situations in which a nucleus contains extra neutrons. Unstable nuclei of this sort will often decay rapidly, with half-lives of a fraction of a second, fast neutrons are usually undesirable in a steady-state nuclear reactor because most fissile fuel has a higher reaction rate with thermal neutrons. Fast neutrons can be changed into thermal neutrons via a process called moderation. This is done through numerous collisions with slower-moving and thus lower-temperature particles like atomic nuclei and these collisions will generally speed up the other particle and slow down the neutron and scatter it. Ideally, a room temperature neutron moderator is used for this process, in reactors heavy water, light water, or graphite are typically used to moderate neutrons. Relativistic Greater than 20 MeV Pile Neutrons of all present in nuclear reactors 0.001 eV to 15 MeV. Ultracold neutrons are free neutrons which can be stored in traps made from certain materials, most fission reactors are thermal reactors that use a neutron moderator to slow down the neutrons produced by nuclear fission. Moderation substantially increases the fission cross section for fissile nuclei such as uranium-235 or plutonium-239, the combination of these effects allows light water reactors to use low-enriched uranium

17.
Fast neutron
–
The neutron detection temperature, also called the neutron energy, indicates a free neutrons kinetic energy, usually given in electron volts. The term temperature is used, since hot, thermal and cold neutrons are moderated in a medium with a certain temperature, the neutron energy distribution is then adopted to the Maxwellian distribution known for thermal motion. Qualitatively, the higher the temperature, the higher the energy of the free neutrons. Kinetic energy, speed and wavelength of the neutron are related through the De Broglie relation, but different ranges with different names are observed in other sources. After a number of collisions with nuclei in a medium at this temperature, neutrons arrive at about this energy level, Neutrons of energy greater than thermal Greater than 0.2 eV Neutrons which are strongly absorbed by cadmium Less than 0.4 eV. Neutrons which are not strongly absorbed by cadmium Greater than 0.6 eV, Neutrons of energy slightly greater than epicadmium neutrons. Refers to neutrons which are strongly susceptible non-fission capture by U-238,1 eV to 300 eV Neutrons that are between slow and fast Few hundred eV to 0.5 MeV. A fast neutron is a neutron with a kinetic energy level close to 1 MeV, hence a speed of 14,000 km/s. They are named fast neutrons to distinguish them from lower-energy thermal neutrons, fast neutrons are produced by nuclear processes, nuclear fission produces neutrons with a mean energy of 2 MeV, which qualifies as fast. Spontaneous fission is a type of decay that some heavy elements undergo. Nuclear fusion, deuterium–tritium fusion produces neutrons of 14.1 MeV that can easily fission uranium-238, neutron emission occurs in very rare situations in which a nucleus contains extra neutrons. Unstable nuclei of this sort will often decay rapidly, with half-lives of a fraction of a second, fast neutrons are usually undesirable in a steady-state nuclear reactor because most fissile fuel has a higher reaction rate with thermal neutrons. Fast neutrons can be changed into thermal neutrons via a process called moderation. This is done through numerous collisions with slower-moving and thus lower-temperature particles like atomic nuclei and these collisions will generally speed up the other particle and slow down the neutron and scatter it. Ideally, a room temperature neutron moderator is used for this process, in reactors heavy water, light water, or graphite are typically used to moderate neutrons. Relativistic Greater than 20 MeV Pile Neutrons of all present in nuclear reactors 0.001 eV to 15 MeV. Ultracold neutrons are free neutrons which can be stored in traps made from certain materials, most fission reactors are thermal reactors that use a neutron moderator to slow down the neutrons produced by nuclear fission. Moderation substantially increases the fission cross section for fissile nuclei such as uranium-235 or plutonium-239, the combination of these effects allows light water reactors to use low-enriched uranium

18.
Fusion neutron
–
The neutron is a subatomic particle, symbol n or n0, with no net electric charge and a mass slightly larger than that of a proton. Protons and neutrons, each with approximately one atomic mass unit, constitute the nucleus of an atom. Their properties and interactions are described by nuclear physics, the nucleus consists of Z protons, where Z is called the atomic number, and N neutrons, where N is the neutron number. The atomic number defines the properties of the atom. The terms isotope and nuclide are often used synonymously, but they are chemical and nuclear concepts, the atomic mass number, symbol A, equals Z+N. For example, carbon has atomic number 6, and its abundant carbon-12 isotope has 6 neutrons, some elements occur in nature with only one stable isotope, such as fluorine. Other elements occur with many stable isotopes, such as tin with ten stable isotopes, even though it is not a chemical element, the neutron is included in the table of nuclides. Within the nucleus, protons and neutrons are bound together through the nuclear force, neutrons are produced copiously in nuclear fission and fusion. They are a contributor to the nucleosynthesis of chemical elements within stars through fission, fusion. The neutron is essential to the production of nuclear power, in the decade after the neutron was discovered in 1932, neutrons were used to induce many different types of nuclear transmutations. These events and findings led to the first self-sustaining nuclear reactor, free neutrons, or individual neutrons free of the nucleus, are effectively a form of ionizing radiation, and as such, are a biological hazard, depending upon dose. A small natural background flux of free neutrons exists on Earth, caused by cosmic ray showers. Dedicated neutron sources like neutron generators, research reactors and spallation sources produce free neutrons for use in irradiation, neutrons and protons are both nucleons, which are attracted and bound together by the nuclear force to form atomic nuclei. The nucleus of the most common isotope of the atom is a lone proton. The nuclei of the hydrogen isotopes deuterium and tritium contain one proton bound to one. All other types of nuclei are composed of two or more protons and various numbers of neutrons. The most common nuclide of the chemical element lead, 208Pb has 82 protons and 126 neutrons. The free neutron has a mass of about 1. 675×10−27 kg, the neutron has a mean square radius of about 0. 8×10−15 m, or 0.8 fm, and it is a spin-½ fermion

19.
Fissile
–
In nuclear engineering, fissile material is material capable of sustaining a nuclear fission chain reaction. By definition, fissile material can sustain a reaction with neutrons of any energy. The predominant neutron energy may be typified by slow neutrons or fast neutrons. Fissile material can be used to fuel thermal-neutron reactors, fast-neutron reactors, according to the fissile rule, for a heavy element with 90 ≤ Z ≤100, its isotopes with 2 × Z − N =43 ±2, with few exceptions, are fissile. A nuclide capable of undergoing fission after capturing a high energy neutron is referred to as fissionable, a fissionable nuclide that can be induced to fission with low-energy thermal neutrons with a high probability is referred to as fissile. Although the terms were formerly synonymous, fissionable materials include also those that can be fissioned only with high-energy neutrons, as a result, fissile materials are a subset of fissionable materials. By contrast, the energy released by uranium-238 absorbing a thermal neutron is less than the critical energy. Consequently, uranium-238 is a material but not a fissile material. As such, while all fissile isotopes are fissionable, not all fissionable isotopes are fissile and these are materials that sustain an explosive fast nuclear fission chain reaction. Under all definitions above, uranium-238 is fissionable, but because it cannot sustain a chain reaction. Fast fission of 238U in the stage of a nuclear weapon contributes greatly to yield. The fast fission of 238U also makes a significant contribution to the output of some fast-neutron reactors. In general, most actinide isotopes with an odd number are fissile. Most nuclear fuels have an odd atomic number, and an even atomic number Z. This implies an odd number of neutrons, isotopes with an odd number of neutrons gain an extra 1 to 2 MeV of energy from absorbing an extra neutron, from the pairing effect which favors even numbers of both neutrons and protons. This energy is enough to supply the extra energy for fission by slower neutrons. They are more likely to ignore the neutron and let it go on its way, or else to absorb the neutron and these even-even isotopes are also less likely to undergo spontaneous fission, and they also have relatively much longer partial half-lives for alpha or beta decay. Examples of these isotopes are uranium-238 and thorium-232, the physical basis for this phenomenon also comes from the pairing effect in nuclear binding energy, but this time from both proton–proton and neutron–neutron pairing

20.
Uranium-233
–
Uranium-233 is a fissile isotope of uranium that is bred from thorium-232 as part of the thorium fuel cycle. Uranium-233 was investigated for use in weapons and as a reactor fuel. It has been used successfully in experimental nuclear reactors and has proposed for much wider use as a nuclear fuel. It has a half-life of 160,000 years, uranium-233 is produced by the neutron irradiation of thorium-232. When thorium-232 absorbs a neutron, it becomes thorium-233, which has a half-life of only 22 minutes, thorium-233 decays into protactinium-233 through beta decay. 233U usually fissions on neutron absorption but sometimes retains the neutron, the capture-to-fission ratio is smaller than the other two major fissile fuels uranium-235 and plutonium-239. In 1946 the public first became informed of U-233 bred from thorium as an available source of nuclear energy and atom bombs, following a United Nations report. The United States produced, over the course of the Cold War, approximately 2 metric tons of uranium-233, in varying levels of chemical and these were produced at the Hanford Site and Savannah River Site in reactors that were designed for the production of plutonium-239. Historical production costs, estimated from the costs of production, were 2–4 million USD/kg. There are few remaining in the world with significant capabilities to produce more uranium-233. Uranium-233 has been used as a fuel in several different reactor types, the long-term strategy of the nuclear power program of India, which has substantial thorium reserves, is to move to a nuclear program breeding uranium-233 from thorium feedstock. The fission of one atom of U-233 generates 197.9 MeV =3.171 × 10−11 J, i. e.19.09 TJ/mol =81.95 TJ/kg. The main difference is the co-presence of uranium-232 which can make uranium-233 very dangerous to work on, although not an outright fizzle, METs actual yield of 22 kilotons was sufficiently below the predicted 33 kt that the information gathered was of limited value. The Soviet Union detonated its first hydrogen bomb the year, the RDS-37. In 1998, as part of its Pokhran-II tests, India detonated an experimental U-233 device of low-yield called Shakti V, the B Reactor and others at the Hanford Site optimized for the production of weapons-grade material have been used to manufacture U-233. The hazards are significant even at 5 parts per million, implosion nuclear weapons require U-232 levels below 50 ppm. Gun-type fission weapons additionally need low levels of impurities, to keep the neutron generation low. The Molten-Salt Reactor Experiment used U-233, bred in light water reactors such as Indian Point Energy Center, thorium, from which U-233 is bred, is roughly three to four times more abundant in the earths crust than uranium

21.
Uranium-235
–
Uranium-235 is an isotope of uranium making up about 0. 72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i. e. it can sustain a chain reaction. It is the fissile isotope that is a primordial nuclide or found in significant quantity in nature. Uranium-235 has a half-life of 703.8 million years and it was discovered in 1935 by Arthur Jeffrey Dempster. Its nuclear cross section for thermal neutrons is about 584.994 barns. For fast neutrons it is on the order of 1 barn, most but not all neutron absorptions result in fission, a minority result in neutron capture forming uranium-236. This is around 2.5 million times more than the energy released from burning coal, uranium enrichment removes some of the uranium-238 and increases the proportion of uranium-235. Highly enriched uranium, which contains a greater proportion of U-235, is sometimes used in nuclear weapon design. If at least one neutron from U-235 fission strikes another nucleus and causes it to fission, if the reaction will sustain itself, it is said to be critical, and the mass of U-235 required to produce the critical condition is said to be a critical mass. A fission chain reaction produces intermediate mass fragments which are highly radioactive, some of them produce neutrons, called delayed neutrons, which contribute to the fission chain reaction. In nuclear reactors, the reaction is slowed down by the addition of control rods which are made of such as boron, cadmium. In nuclear bombs, the reaction is uncontrolled and the amount of energy released creates a nuclear explosion. The Little Boy gun type atomic bomb dropped on Hiroshima on August 6,1945 was made of enriched uranium with a large tamper. The nominal spherical critical mass for an untampered 235U nuclear weapon is 56 kilograms, the material must be 85% or more of 235U and is known as weapons grade uranium, though for a crude, inefficient weapon 20% is sufficient. Even lower enrichment can be used, but then the critical mass rapidly increases. Most modern nuclear weapon designs use plutonium as the component of the primary stage. Uranium-235 has many such as fuel for nuclear power plants. DOE Fundamentals handbook, Nuclear Physics and Reactor theory Vol.1, Vol.2

22.
Uranium-238
–
Uranium-238 is the most common isotope of uranium found in nature, making up over 99% of it. Unlike uranium-235 it is non-fissile, which means it cannot sustain a chain reaction, however, it is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239. 238U cannot support a chain reaction because inelastic scattering reduces neutron energy below the range where fast fission of one or more next-generation nuclei is probable. Doppler broadening of U-238s neutron absorption resonances, increasing absorption as fuel increases, is also an essential negative feedback mechanism for reactor control. Around 99. 284% of natural uranium is uranium-238, which has a half-life of 1. 41×1017 seconds, depleted uranium has an even higher concentration of the 238U isotope, and even low-enriched uranium, while having a higher proportion of the uranium-235 isotope, is still mostly 238U. In a fission reactor, uranium-238 can be used to generate 239Pu. In a typical nuclear reactor, up to one-third of the power does come from the fission of 239Pu, which is not supplied as a fuel to the reactor. 238U is not usable directly as fuel, though it can produce energy via fast fission. In this process, a neutron that has an energy in excess of 1 MeV can cause the nucleus of 238U to split in two. 238U can be used as a material for creating plutonium-239. Breeder reactors carry out such a process of transmutation to convert the fertile isotope 238U into fissile Pu-239 and it has been estimated that there is anywhere from 10,000 to five billion years worth of 238U for use in these power plants. Breeder technology has been used in experimental nuclear reactors. By December 2005, the breeder reactor producing power was the 600-megawatt BN-600 reactor at the Beloyarsk Nuclear Power Station in Russia. Russia has planned to build another unit, BN-800, at the Beloyarsk nuclear power plant, also, Japans Monju breeder reactor is planned to be started, having been shut down since 1995, and both China and India have announced plans to build nuclear breeder reactors. The breeder reactor as its name implies creates even larger quantities of Pu-239 than the nuclear reactor. This design is still in the stages of development. It is not as effective as ordinary water for stopping fast neutrons, both metallic depleted uranium and depleted uranium dioxide are used for radiation shielding. Uranium is about five times better as a ray shield than lead

23.
Plutonium-239
–
Plutonium-239 is an isotope of plutonium. Plutonium-239 is the fissile isotope used for the production of nuclear weapons. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in thermal spectrum reactors, along with uranium-235. Plutonium-239 has a half-life of 24,110 years, plutonium-239 can also absorb neutrons and fission along with the uranium-235 in a reactor. Of all the common nuclear fuels, Pu-239 has the smallest critical mass, a spherical untamped critical mass is about 11 kg,10.2 cm in diameter. Using appropriate triggers, neutron reflectors, implosion geometry and tampers and this optimization usually requires a large nuclear development organization supported by a sovereign nation. The fission of one atom of Pu-239 generates 207.1 MeV =3.318 × 10−11 J, i. e.19.98 TJ/mol =83.61 TJ/kg, or about 2322719 kilowatt hours/kg. Pu-239 is normally created in nuclear reactors by transmutation of atoms of one of the isotopes of uranium present in the fuel rods. Occasionally, when an atom of U-238 is exposed to radiation, its nucleus will capture a neutron. This happens more easily with lower kinetic energy, the U-239 then rapidly undergoes two beta decays, becoming Pu-239.5 m i n β −93239 N p →2. Only if the fuel has been exposed for a few days in the reactor, Pu-239 has a higher probability for fission than U-235 and a larger number of neutrons produced per fission event, so it has a smaller critical mass. In practice, however, reactor-bred plutonium will invariably contain an amount of Pu-240 due to the tendency of Pu-239 to absorb an additional neutron during production. Pu-240 has a rate of spontaneous fission events, making it an undesirable contaminant. It is because of this limitation that plutonium-based weapons must be implosion-type, moreover, Pu-239 and Pu-240 cannot be chemically distinguished, so expensive and difficult isotope separation would be necessary to separate them. Weapons-grade plutonium is defined as containing no more than 7% Pu-240, Pu-240 exposed to alpha particles will incite a nuclear fission. A reactor running on unenriched or moderately enriched uranium contains a great deal of U-238, however, most commercial nuclear power reactor designs require the entire reactor to shut down, often for weeks, in order to change the fuel elements. They therefore produce plutonium in a mix of isotopes that is not well-suited to weapon construction, in practice, their construction and operation is sufficiently difficult that they are generally only used to produce plutonium. Breeder reactors are generally fast reactors, since fast neutrons are more efficient at plutonium production

24.
Plutonium-241
–
Plutonium-241 is an isotope of plutonium formed when plutonium-240 captures a neutron. Like Pu-239 but unlike 240Pu, 241Pu is fissile, with a neutron cross section about 1/3 greater than 239Pu. In the non-fission case, neutron capture produces plutonium-242, in general, isotopes with an odd number of neutrons are both more likely to absorb a neutron, and more likely to undergo fission on neutron absorption, than isotopes with an even number of neutrons. 241Pu has a half-life of 14 years, corresponding to a decay of about 5% of Pu-241 nuclei over a one-year period, in a thermal reactor, 241Am captures a neutron to become americium-242, which quickly becomes curium-242 via beta decay. In short, Am-241 needs to absorb two neutrons before again becoming a fissile isotope

25.
Radioisotope
–
A radionuclide is an atom that has excess nuclear energy, making it unstable. During those processes, the radionuclide is said to undergo radioactive decay, the unstable nucleus is more stable following the emission, but will sometimes undergo further decay. Radioactive decay is a process at the level of single atoms. However, for a collection of atoms of an element the decay rate. The range of the half-lives of radioactive atoms have no known limits, Radionuclides occur naturally and are artificially produced in nuclear reactors, cyclotrons, particle accelerators or radionuclide generators. There are about 730 radionuclides with half-lives longer than 60 minutes, with the longest half lives are the 32 primordial radionuclides that have survived from the creation of the Solar System. Over 60 further radionuclides are detectable in nature, either as daughters of these, more than 2400 radionuclides have half-lives less than 60 minutes. Most of those are produced artificially, and have very short half-lives. For comparison, there are about 254 stable nuclides, even the lightest element, hydrogen, has a well-known radionuclide, tritium. Elements heavier than lead, and the elements technetium and promethium, unplanned exposure to radionuclides generally has a harmful effect on living organisms including humans, although low levels of exposure occur naturally without harm. However, radionuclides with suitable properties are used in medicine for both diagnosis and treatment. An imaging tracer made with radionuclides is called a radioactive tracer, a pharmaceutical drug made with radionuclides is called a radiopharmaceutical. On Earth, naturally occurring radionuclides fall into three categories, primordial radionuclides, secondary radionuclides, and cosmogenic radionuclides, Radionuclides are produced in stellar nucleosynthesis and supernova explosions along with stable nuclides. Most decay quickly but can still be observed astronomically and can play a part in understanding astronomic processes, primordial radionuclides, such as uranium and thorium, exist in the present time because their half-lives are so long they have not yet completely decayed. It is possible decay may be observed in other nuclides adding to this list of primordial radionuclides, secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides and they arise in the decay chain of the primordial isotopes thorium-232, uranium-238 and uranium-235. Examples include the natural isotopes of polonium and radium, cosmogenic isotopes, such as carbon-14, are present because they are continually being formed in the atmosphere due to cosmic rays. Many of these radionuclides exist only in trace amounts in nature, secondary radionuclides will occur in proportion to their half-lives, so short-lived ones will be very rare

26.
Halflife
–
Half-life is the time required for a quantity to reduce to half its initial value. The term is used in nuclear physics to describe how quickly unstable atoms undergo. The term is used more generally to characterize any type of exponential or non-exponential decay. For example, the medical sciences refer to the biological half-life of drugs, the converse of half-life is doubling time. The original term, half-life period, dating to Ernest Rutherfords discovery of the principle in 1907, was shortened to half-life in the early 1950s. Rutherford applied the principle of a radioactive elements half-life to studies of age determination of rocks by measuring the period of radium to lead-206. Half-life is constant over the lifetime of an exponentially decaying quantity, the accompanying table shows the reduction of a quantity as a function of the number of half-lives elapsed. A half-life usually describes the decay of discrete entities, such as radioactive atoms, in that case, it does not work to use the definition that states half-life is the time required for exactly half of the entities to decay. For example, if there are 3 radioactive atoms with a half-life of one second, instead, the half-life is defined in terms of probability, Half-life is the time required for exactly half of the entities to decay on average. In other words, the probability of a radioactive atom decaying within its half-life is 50%, for example, the image on the right is a simulation of many identical atoms undergoing radioactive decay. Note that after one half-life there are not exactly one-half of the remaining, only approximately. Nevertheless, when there are many identical atoms decaying, the law of large numbers suggests that it is a good approximation to say that half of the atoms remain after one half-life. There are various simple exercises that demonstrate probabilistic decay, for example involving flipping coins or running a computer program. The three parameters t1⁄2, τ, and λ are all related in the following way. Amount approaches zero as t approaches infinity as expected, some quantities decay by two exponential-decay processes simultaneously. There is a half-life describing any exponential-decay process, for example, The current flowing through an RC circuit or RL circuit decays with a half-life of RCln or lnL/R, respectively. For this example, the half time might be used instead of half life. In a first-order chemical reaction, the half-life of the reactant is ln/λ, in radioactive decay, the half-life is the length of time after which there is a 50% chance that an atom will have undergone nuclear decay

27.
Gamma radiation
–
Gamma ray, denoted by the lower-case Greek letter gamma, is penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei. It consists of photons in the highest observed range of photon energy, paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays, Rutherford had previously discovered two other types of radioactive decay, which he named alpha and beta rays. Gamma rays are able to ionize atoms, and are thus biologically hazardous. The decay of a nucleus from a high energy state to a lower energy state. Natural sources of gamma rays on Earth are observed in the decay of radionuclides. There are rare terrestrial natural sources, such as lightning strikes and terrestrial gamma-ray flashes, However, a large fraction of such astronomical gamma rays are screened by Earths atmosphere and can only be detected by spacecraft. Gamma rays typically have frequencies above 10 exahertz, and therefore have energies above 100 keV and wavelengths less than 10 picometers, However, this is not a strict definition, but rather only a rule-of-thumb description for natural processes. Electromagnetic radiation from radioactive decay of nuclei is referred to as gamma rays no matter its energy. This radiation commonly has energy of a few hundred keV, in astronomy, gamma rays are defined by their energy, and no production process needs to be specified. The energies of gamma rays from astronomical sources range to over 10 TeV, a notable example is the extremely powerful bursts of high-energy radiation referred to as long duration gamma-ray bursts, of energies higher than can be produced by radioactive decay. These bursts of gamma rays are thought to be due to the collapse of stars called hypernovae, the first gamma ray source to be discovered historically was the radioactive decay process called gamma decay. In this type of decay, a nucleus emits a gamma ray almost immediately upon formation. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, However, Villard did not consider naming them as a different fundamental type. Rutherford also noted that gamma rays were not deflected by a field, another property making them unlike alpha. Gamma rays were first thought to be particles with mass, like alpha, Rutherford initially believed that they might be extremely fast beta particles, but their failure to be deflected by a magnetic field indicated that they had no charge. In 1914, gamma rays were observed to be reflected from crystal surfaces, Rutherford and his coworker Edward Andrade measured the wavelengths of gamma rays from radium, and found that they were similar to X-rays, but with shorter wavelengths and higher frequency. This was eventually recognized as giving them more energy per photon

28.
Nuclear power plant
–
A nuclear power plant or nuclear power station is a thermal power station in which the heat source is a nuclear reactor. As is typical in all conventional thermal power stations the heat is used to steam which drives a steam turbine connected to an electric generator which produces electricity. As of 23 April 2014, the IAEA report there are 449 nuclear power reactors in operation operating in 31 countries, Nuclear power stations are usually considered to be base load stations, since fuel is a small part of the cost of production. Their operations and maintenance and fuel costs are, along with stations, at the low end of the spectrum. The cost of spent fuel management, however, is somewhat uncertain, for more history, see nuclear reactor, nuclear power and nuclear fission. The second, larger experiment occurred on December 20,1951 at the EBR-I experimental station near Arco, on June 27,1954, the worlds first nuclear power station to generate electricity for a power grid started operations at the Soviet city of Obninsk. The worlds first full power station, Calder Hall in England. The worlds first full power station solely devoted to electricity production, Shippingport power plant in the United States. The conversion to electrical energy takes place indirectly, as in conventional power stations. The fission in a nuclear reactor heats the reactor coolant, the coolant may be water or gas or even liquid metal depending on the type of reactor. The reactor coolant then goes to a generator and heats water to produce steam. The pressurized steam is then fed to a multi-stage steam turbine. After the steam turbine has expanded and partially condensed the steam, the condenser is a heat exchanger which is connected to a secondary side such as a river or a cooling tower. The water is pumped back into the steam generator and the cycle begins again. The water-steam cycle corresponds to the Rankine cycle, the nuclear reactor is the heart of the station. In its central part, the cores heat is generated by controlled nuclear fission. With this heat, a coolant is heated as it is pumped through the reactor, heat from nuclear fission is used to raise steam, which runs through turbines, which in turn powers the electrical generators. Nuclear reactors usually rely on uranium to fuel the chain reaction, Uranium is a very heavy metal that is abundant on Earth and is found in sea water as well as most rocks

29.
Slow neutron
–
The neutron detection temperature, also called the neutron energy, indicates a free neutrons kinetic energy, usually given in electron volts. The term temperature is used, since hot, thermal and cold neutrons are moderated in a medium with a certain temperature, the neutron energy distribution is then adopted to the Maxwellian distribution known for thermal motion. Qualitatively, the higher the temperature, the higher the energy of the free neutrons. Kinetic energy, speed and wavelength of the neutron are related through the De Broglie relation, but different ranges with different names are observed in other sources. After a number of collisions with nuclei in a medium at this temperature, neutrons arrive at about this energy level, Neutrons of energy greater than thermal Greater than 0.2 eV Neutrons which are strongly absorbed by cadmium Less than 0.4 eV. Neutrons which are not strongly absorbed by cadmium Greater than 0.6 eV, Neutrons of energy slightly greater than epicadmium neutrons. Refers to neutrons which are strongly susceptible non-fission capture by U-238,1 eV to 300 eV Neutrons that are between slow and fast Few hundred eV to 0.5 MeV. A fast neutron is a neutron with a kinetic energy level close to 1 MeV, hence a speed of 14,000 km/s. They are named fast neutrons to distinguish them from lower-energy thermal neutrons, fast neutrons are produced by nuclear processes, nuclear fission produces neutrons with a mean energy of 2 MeV, which qualifies as fast. Spontaneous fission is a type of decay that some heavy elements undergo. Nuclear fusion, deuterium–tritium fusion produces neutrons of 14.1 MeV that can easily fission uranium-238, neutron emission occurs in very rare situations in which a nucleus contains extra neutrons. Unstable nuclei of this sort will often decay rapidly, with half-lives of a fraction of a second, fast neutrons are usually undesirable in a steady-state nuclear reactor because most fissile fuel has a higher reaction rate with thermal neutrons. Fast neutrons can be changed into thermal neutrons via a process called moderation. This is done through numerous collisions with slower-moving and thus lower-temperature particles like atomic nuclei and these collisions will generally speed up the other particle and slow down the neutron and scatter it. Ideally, a room temperature neutron moderator is used for this process, in reactors heavy water, light water, or graphite are typically used to moderate neutrons. Relativistic Greater than 20 MeV Pile Neutrons of all present in nuclear reactors 0.001 eV to 15 MeV. Ultracold neutrons are free neutrons which can be stored in traps made from certain materials, most fission reactors are thermal reactors that use a neutron moderator to slow down the neutrons produced by nuclear fission. Moderation substantially increases the fission cross section for fissile nuclei such as uranium-235 or plutonium-239, the combination of these effects allows light water reactors to use low-enriched uranium

30.
Pu-239
–
Plutonium-239 is an isotope of plutonium. Plutonium-239 is the fissile isotope used for the production of nuclear weapons. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in thermal spectrum reactors, along with uranium-235. Plutonium-239 has a half-life of 24,110 years, plutonium-239 can also absorb neutrons and fission along with the uranium-235 in a reactor. Of all the common nuclear fuels, Pu-239 has the smallest critical mass, a spherical untamped critical mass is about 11 kg,10.2 cm in diameter. Using appropriate triggers, neutron reflectors, implosion geometry and tampers and this optimization usually requires a large nuclear development organization supported by a sovereign nation. The fission of one atom of Pu-239 generates 207.1 MeV =3.318 × 10−11 J, i. e.19.98 TJ/mol =83.61 TJ/kg, or about 2322719 kilowatt hours/kg. Pu-239 is normally created in nuclear reactors by transmutation of atoms of one of the isotopes of uranium present in the fuel rods. Occasionally, when an atom of U-238 is exposed to radiation, its nucleus will capture a neutron. This happens more easily with lower kinetic energy, the U-239 then rapidly undergoes two beta decays, becoming Pu-239.5 m i n β −93239 N p →2. Only if the fuel has been exposed for a few days in the reactor, Pu-239 has a higher probability for fission than U-235 and a larger number of neutrons produced per fission event, so it has a smaller critical mass. In practice, however, reactor-bred plutonium will invariably contain an amount of Pu-240 due to the tendency of Pu-239 to absorb an additional neutron during production. Pu-240 has a rate of spontaneous fission events, making it an undesirable contaminant. It is because of this limitation that plutonium-based weapons must be implosion-type, moreover, Pu-239 and Pu-240 cannot be chemically distinguished, so expensive and difficult isotope separation would be necessary to separate them. Weapons-grade plutonium is defined as containing no more than 7% Pu-240, Pu-240 exposed to alpha particles will incite a nuclear fission. A reactor running on unenriched or moderately enriched uranium contains a great deal of U-238, however, most commercial nuclear power reactor designs require the entire reactor to shut down, often for weeks, in order to change the fuel elements. They therefore produce plutonium in a mix of isotopes that is not well-suited to weapon construction, in practice, their construction and operation is sufficiently difficult that they are generally only used to produce plutonium. Breeder reactors are generally fast reactors, since fast neutrons are more efficient at plutonium production

31.
Fast reactor
–
A fast neutron reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons. Such a reactor needs no moderator, but must use fuel that is relatively rich in fissile material when compared to that required for a thermal reactor. In order to sustain a chain reaction, the neutrons released in fission events have to react with other atoms in the fuel. The chance of this depends on the energy of the neutron, most atoms will only undergo induced fission with high energy neutrons. Natural uranium consists mostly of three isotopes, U-238, U-235, and trace quantities of U-234, a product of U-238. U-238 accounts for roughly 99. 3% of natural uranium and undergoes fission only by neutrons with energies of 5 MeV or greater, about 0. 7% of natural uranium is U-235, which undergoes fission by neutrons of any energy, but particularly by lower energy neutrons. When either of these isotopes undergoes fission they release neutrons around 1 to 2 MeV, too low to cause fission in U-238, and too high to do so easily in U-235. The common solution to this problem is to slow the neutron from these fast speeds using a moderator, any substance which interacts with the neutrons. The most common moderator is normal water, which slows the neutrons through elastic scattering until the neutrons reach thermal equilibrium with the water. Although U-238 will not undergo fission by the released in fission. Pu-239 has a cross section very similar to that of U-235. In most reactors this accounts for as much as ⅓ of the energy being generated, not all of the Pu-239 is burned up during normal operation, and the leftover, along with leftover U-238, can be separated out to be used in new fuel during nuclear reprocessing. Water is a moderator for practical reasons, but has its disadvantages. From a nuclear standpoint, the problem is that water can absorb a neutron. The most common solution to this problem is to concentrate the amount of U-235 in the fuel to produce enriched uranium. Other designs use different moderators, like water, that are much less likely to absorb neutrons. In either case, the neutron economy is based on thermal neutrons. Although U-235 and Pu-239 are less sensitive to higher energy neutrons and this means that if you enrich the fuel you will eventually reach a threshold where there are enough fissile atoms in the fuel that a chain reaction can be maintained even with fast neutrons

32.
Nuclear weapon
–
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from small amounts of matter. The first test of a bomb released the same amount of energy as approximately 20,000 tons of TNT. The first thermonuclear bomb test released the same amount of energy as approximately 10 million tons of TNT, a thermonuclear weapon weighing little more than 2,400 pounds can produce an explosive force comparable to the detonation of more than 1.2 million tons of TNT. A nuclear device no larger than traditional bombs can devastate a city by blast, fire. Nuclear weapons are considered weapons of destruction, and their use. Nuclear weapons have been used twice in nuclear warfare, both times by the United States against Japan near the end of World War II, the bombings resulted in the deaths of approximately 200,000 civilians and military personnel from acute injuries sustained from the explosions. The ethics of the bombings and their role in Japans surrender remain the subject of scholarly, since the atomic bombings of Hiroshima and Nagasaki, nuclear weapons have been detonated on over two thousand occasions for the purposes of testing and demonstration. Only a few nations possess such weapons or are suspected of seeking them, israel is also believed to possess nuclear weapons, though in a policy of deliberate ambiguity, it does not acknowledge having them. Germany, Italy, Turkey, Belgium and the Netherlands are nuclear weapons sharing states, south Africa is the only country to have independently developed and then renounced and dismantled its nuclear weapons. Modernisation of weapons continues to occur, all existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Weapons whose explosive output is exclusively from fission reactions are commonly referred to as bombs or atom bombs. This has long noted as something of a misnomer, as their energy comes from the nucleus of the atom. The latter approach is considered more sophisticated than the former and only the approach can be used if the fissile material is plutonium. A major challenge in all nuclear weapon designs is to ensure that a significant fraction of the fuel is consumed before the weapon destroys itself. The amount of energy released by fission bombs can range from the equivalent of just under a ton to upwards of 500,000 tons of TNT, all fission reactions necessarily generate fission products, the radioactive remains of the atomic nuclei split by the fission reactions. Many fission products are highly radioactive or moderately radioactive. Fission products are the radioactive component of nuclear fallout

33.
Minor actinides
–
The minor actinides are the actinide elements in used nuclear fuel other than uranium and plutonium, which are termed the major actinides. The minor actinides include neptunium, americium, curium, berkelium, californium, einsteinium, the most important isotopes in spent nuclear fuel are neptunium-237, americium-241, americium-243, curium-242 through -248, and californium-249 through -252. Plutonium and the minor actinides will be responsible for the bulk of the radiotoxicity, the plutonium from a power reactor tends to have a greater amount of Pu-241 than the plutonium generated by the lower burnup operations designed to create weapons-grade plutonium. Because the reactor-grade plutonium contains so much Pu-241 the presence of americium-241 makes the plutonium less suitable for making a nuclear weapon. The ingrowth of americium in plutonium is one of the methods for identifying the origin of a sample of plutonium. Americium is commonly used in industry as both a particle and low photon energy gamma radiation source. For instance it is used in smoke detectors. Americium can be formed by neutron capture of Pu-239 and Pu-240 forming Pu-241 which then decays by beta decay to Am-241, in general, as the energy of the neutrons increases, the ratio of the fission cross section to the neutron capture cross section changes in favour of fission. Hence if MOX is used in a thermal reactor such as a boiling water reactor or pressurized water reactor then more americium can be expected in the fuel than that from a fast neutron reactor. Some of them have found in fallout from bomb tests. See Actinides in the environment for details of the actinides in the environment

34.
Californium
–
Californium is a radioactive metallic chemical element with symbol Cf and atomic number 98. The element was first made in 1950 at the University of California Radiation Laboratory in Berkeley, the element was named after the university and the state of California. Two crystalline forms exist for californium under normal pressure, one above, a third form exists at high pressure. Californium slowly tarnishes in air at room temperature, Compounds of californium are dominated by a chemical form of the element, designated californium, that can participate in three chemical bonds. The most stable of californiums twenty known isotopes is californium-251, which has a half-life of 898 years and this short half-life means the element is not found in significant quantities in the Earths crust. Californium is one of the few elements that have practical applications. Most of these applications exploit the property of certain isotopes of californium to emit neutrons, for example, californium can be used to help start up nuclear reactors, and it is employed as a source of neutrons when studying materials with neutron diffraction and neutron spectroscopy. Californium can also be used in synthesis of higher mass elements. Users of californium must take into account radiological concerns and the ability to disrupt the formation of red blood cells by bioaccumulating in skeletal tissue. Californium is a silvery white metal with a melting point of 900 ±30 °C. The pure metal is malleable and is cut with a razor blade. Californium metal starts to vaporize above 300 °C when exposed to a vacuum, below 51 K californium metal is either ferromagnetic or ferrimagnetic, between 48 and 66 K it is antiferromagnetic, and above 160 K it is paramagnetic. It forms alloys with lanthanide metals but little is known about them, the element has two crystalline forms under 1 standard atmosphere of pressure, A double-hexagonal close-packed form dubbed alpha and a face-centered cubic form designated beta. The α form exists below 600–800 °C with a density of 15.10 g/cm3, at 48 GPa of pressure the β form changes into an orthorhombic crystal system due to delocalization of the atoms 5f electrons, which frees them to bond. The bulk modulus of a material is a measure of its resistance to uniform pressure, californiums bulk modulus is 50 ±5 GPa, which is similar to trivalent lanthanide metals but smaller than more familiar metals, such as aluminium. Californium exhibits oxidation states of 4,3, or 2 and it typically forms eight or nine bonds to surrounding atoms or ions. Its chemical properties are predicted to be similar to other primarily 3+ valence actinide elements and the element dysprosium, the element slowly tarnishes in air at room temperature, with the rate increasing when moisture is added. Californium reacts when heated with hydrogen, nitrogen, or a chalcogen, reactions with dry hydrogen, Californium is only water-soluble as the californium cation

35.
Proton
–
A proton is a subatomic particle, symbol p or p+, with a positive electric charge of +1e elementary charge and mass slightly less than that of a neutron. Protons and neutrons, each with masses of one atomic mass unit, are collectively referred to as nucleons. One or more protons are present in the nucleus of every atom, the number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number. Since each element has a number of protons, each element has its own unique atomic number. The word proton is Greek for first, and this name was given to the nucleus by Ernest Rutherford in 1920. In previous years, Rutherford had discovered that the nucleus could be extracted from the nuclei of nitrogen by atomic collisions. Protons were therefore a candidate to be a particle, and hence a building block of nitrogen. In the modern Standard Model of particle physics, protons are hadrons, and like neutrons, although protons were originally considered fundamental or elementary particles, they are now known to be composed of three valence quarks, two up quarks and one down quark. The rest masses of quarks contribute only about 1% of a protons mass, the remainder of a protons mass is due to quantum chromodynamics binding energy, which includes the kinetic energy of the quarks and the energy of the gluon fields that bind the quarks together. At sufficiently low temperatures, free protons will bind to electrons, however, the character of such bound protons does not change, and they remain protons. A fast proton moving through matter will slow by interactions with electrons and nuclei, the result is a protonated atom, which is a chemical compound of hydrogen. In vacuum, when electrons are present, a sufficiently slow proton may pick up a single free electron, becoming a neutral hydrogen atom. Such free hydrogen atoms tend to react chemically with other types of atoms at sufficiently low energies. When free hydrogen atoms react with other, they form neutral hydrogen molecules. Protons are spin-½ fermions and are composed of three quarks, making them baryons. Protons have an exponentially decaying positive charge distribution with a mean square radius of about 0.8 fm. Protons and neutrons are both nucleons, which may be together by the nuclear force to form atomic nuclei. The nucleus of the most common isotope of the atom is a lone proton

36.
Neutron
–
The neutron is a subatomic particle, symbol n or n0, with no net electric charge and a mass slightly larger than that of a proton. Protons and neutrons, each with approximately one atomic mass unit, constitute the nucleus of an atom. Their properties and interactions are described by nuclear physics, the nucleus consists of Z protons, where Z is called the atomic number, and N neutrons, where N is the neutron number. The atomic number defines the properties of the atom. The terms isotope and nuclide are often used synonymously, but they are chemical and nuclear concepts, the atomic mass number, symbol A, equals Z+N. For example, carbon has atomic number 6, and its abundant carbon-12 isotope has 6 neutrons, some elements occur in nature with only one stable isotope, such as fluorine. Other elements occur with many stable isotopes, such as tin with ten stable isotopes, even though it is not a chemical element, the neutron is included in the table of nuclides. Within the nucleus, protons and neutrons are bound together through the nuclear force, neutrons are produced copiously in nuclear fission and fusion. They are a contributor to the nucleosynthesis of chemical elements within stars through fission, fusion. The neutron is essential to the production of nuclear power, in the decade after the neutron was discovered in 1932, neutrons were used to induce many different types of nuclear transmutations. These events and findings led to the first self-sustaining nuclear reactor, free neutrons, or individual neutrons free of the nucleus, are effectively a form of ionizing radiation, and as such, are a biological hazard, depending upon dose. A small natural background flux of free neutrons exists on Earth, caused by cosmic ray showers. Dedicated neutron sources like neutron generators, research reactors and spallation sources produce free neutrons for use in irradiation, neutrons and protons are both nucleons, which are attracted and bound together by the nuclear force to form atomic nuclei. The nucleus of the most common isotope of the atom is a lone proton. The nuclei of the hydrogen isotopes deuterium and tritium contain one proton bound to one. All other types of nuclei are composed of two or more protons and various numbers of neutrons. The most common nuclide of the chemical element lead, 208Pb has 82 protons and 126 neutrons. The free neutron has a mass of about 1. 675×10−27 kg, the neutron has a mean square radius of about 0. 8×10−15 m, or 0.8 fm, and it is a spin-½ fermion

37.
Beta decay
–
In nuclear physics, beta decay is a type of radioactive decay in which a beta ray, and a neutrino are emitted from an atomic nucleus. Neither the beta particle nor its associated neutrino exist within the prior to beta decay. By this process, unstable atoms obtain a more stable ratio of protons to neutrons, the probability of a nuclide decaying due to beta and other forms of decay is determined by its binding energy. The binding energies of all existing nuclides form what is called the valley of stability. Beta decay is a consequence of the force, which is characterized by relatively lengthy decay times. Nucleons are composed of up or down quarks, and the force allows a quark to change type by the exchange of a W boson. For example, a neutron, composed of two quarks and an up quark, decays to a proton composed of a down quark. Decay times for many nuclides that are subject to beta decay can be thousands of years, electron capture is sometimes included as a type of beta decay, because the basic nuclear process, mediated by the weak force, is the same. In electron capture, an atomic electron is captured by a proton in the nucleus, transforming it into a neutron. The two types of decay are known as beta minus and beta plus. β+ decay is known as positron emission. Beta decay conserves a number known as the lepton number, or the number of electrons. These particles have lepton number +1, while their antiparticles have lepton number −1, since a proton or neutron has lepton number zero, β+ decay must be accompanied with an electron neutrino, while β− decay must be accompanied by an electron antineutrino. This new element has a mass number A, but an atomic number Z that is increased by one. As in all nuclear decays, the element is known as the parent nuclide while the resulting element is known as the daughter nuclide. The beta spectrum, or distribution of values for the beta particles, is continuous. The total energy of the process is divided between the electron, the antineutrino, and the recoiling nuclide. In the figure to the right, an example of an electron with 0.40 MeV energy from the decay of 210Bi is shown

38.
Proton emission
–
Proton emission is a rare type of radioactive decay in which a proton is ejected from a nucleus. For a proton to escape a nucleus, the proton separation energy must be negative - the proton is therefore unbound, Proton emission is not seen in naturally occurring isotopes, proton emitters can be produced via nuclear reactions, usually using linear particle accelerators. Research in the field flourished after this breakthrough, and to more than 25 isotopes have been found to exhibit proton emission. The study of proton emission has aided the understanding of nuclear deformation, masses and structure, in 2002, the simultaneous emission of two protons was observed from the nucleus iron-45 in experiments at GSI and GANIL. In 2005 it was determined that zinc-54 can also undergo double proton decay. Proton drip line Diproton Free neutron Neutron emission Nuclear Structure and Decay Data - IAEA with query on Proton Separation Energy

39.
Electron capture
–
Electron capture is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shell. This process thereby changes a proton to a neutron and simultaneously causes the emission of an electron neutrino. P + e− → n + ν e The daughter nuclide, if it is in an excited state, usually, a gamma ray is emitted during this transition, but nuclear de-excitation may also take place by internal conversion. Following capture of an electron from the atom, an outer electron replaces the electron that was captured. Following electron capture, the number is reduced by one, the neutron number is increased by one. Simple electron capture results in an atom, since the loss of the electron in the electron shell is balanced by a loss of positive nuclear charge. However, an atomic ion may result from further Auger electron emission. Electron capture is an example of interaction, one of the four fundamental forces. Electron capture is always an alternate mode for radioactive isotopes that do have sufficient energy to decay by positron emission. It is sometimes called Inverse beta decay, though this term can refer to the interaction of an electron antineutrino with a proton. For example, rubidium-83 will decay to krypton-83 solely by electron capture, the theory of electron capture was first discussed by Gian-Carlo Wick in a 1934 paper, and then developed by Hideki Yukawa and others. K-electron capture was first observed by Luis Alvarez, in vanadium-48 and he reported it in a 1937 paper in Physical Review. Alvarez went on to study electron capture in gallium-67 and other nuclides, radioactive isotopes that decay by pure electron capture can be inhibited from radioactive decay if they are fully ionized. Anomalies in elemental distributions are thought to be partly a result of this effect on electron capture, chemical bonds can also affect the rate of electron capture to a small degree depending on the proximity of electrons to the nucleus. For example, in 7Be, a difference of 0. 9% has been observed between half-lives in metallic and insulating environments and this relatively large effect is due to the fact that beryllium is a small atom whose valence electrons are close to the nucleus. Electron capture happens most often in the heavier neutron-deficient elements where the change is smallest. When the loss of mass in a reaction is greater than zero but less than 2m. Some common radioisotopes that decay by electron capture include, For a full list, the LIVEChart of Nuclides - IAEA with filter on electron capture

40.
Observationally Stable
–
Stable nuclides are nuclides that are not radioactive and so do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, the 80 elements with one or more stable isotopes comprise a total of 254 nuclides that have not been known to decay using current equipment. Of these elements,26 have only one isotope, they are thus termed monoisotopic. The rest have more than one stable isotope, tin has ten stable isotopes, the largest number known for an element. Most naturally occurring nuclides are stable, and about 32 more are known radioactives with sufficiently long half-lives to occur primordially. If the half-life of a nuclide is comparable to, or greater than, the Earths age, a significant amount will have survived since the formation of the Solar System and it will then contribute in that way to the natural isotopic composition of a chemical element. Primordially present radioisotopes are easily detected with half-lives as short as 700 million years and this is the present limit of detection, as shorter-lived nuclides have not yet been detected undisputedly in nature. Some isotopes that are classed as stable are predicted to have extremely long half-lives, 209Bi and 180W were formerly classed as stable, but have been recently found to be alpha-active. However, such nuclides do not change their status as primordial when they are found to be radioactive. Most stable isotopes in the earth are believed to have formed in processes of nucleosynthesis, either in the Big Bang. However, some stable isotopes also show abundance variations in the earth as a result of decay from long-lived radioactive nuclides and these decay-products are termed radiogenic isotopes, in order to distinguish them from the much larger group of non-radiogenic isotopes. The so-called island of stability may reveal a number of long-lived or even stable atoms that are heavier than lead, of the known chemical elements,80 elements have at least one stable nuclide. These comprise the first 82 elements from hydrogen to lead, with the two exceptions, technetium and promethium, that do not have any stable nuclides, as of December 2011, there were a total of 254 known stable nuclides. In this definition, stable means a nuclide that has never observed to decay against the natural background. Thus, these elements have half lives too long to be measured by any means and these last 26 are thus called monoisotopic elements. The mean number of isotopes for elements which have at least one stable isotope is 254/80 =3.2. Stability of isotopes is affected by the ratio of protons to neutrons, as in the case of tin, a magic number for Z, the atomic number, tends to increase the number of stable isotopes for the element. Just as in the case of electrons, which have the lowest energy state when they occur in pairs in an orbital, nucleons exhibit a lower energy state when their number is even

Isotope
–
Isotopes are variants of a particular chemical element which differ in neutron number. All isotopes of an element have the same number of protons in each atom. The number of protons within the nucleus is called atomic number and is equal to the number of electrons in the neutral atom. Each atomic number identifies a specific element, but not the is

1.
The three naturally-occurring isotopes of hydrogen. The fact that each isotope has one proton makes them all variants of hydrogen: the identity of the isotope is given by the number of neutrons. From left to right, the isotopes are protium (1 H) with zero neutrons, deuterium (2 H) with one neutron, and tritium (3 H) with two neutrons.

2.
Nuclear physics

3.
In the bottom right corner of J. J. Thomson 's photographic plate are the separate impact marks for the two isotopes of neon: neon-20 and neon-22.

Radioactive decay
–
A material containing such unstable nuclei is considered radioactive. Certain highly excited short-lived nuclear states can decay through neutron emission, or more rarely, however, for a collection of atoms, the collections expected decay rate is characterized in terms of their measured decay constants or half-lives. This is the basis of radiometri

1.
Pierre and Marie Curie in their Paris laboratory, before 1907

2.
Alpha decay is one type of radioactive decay, in which an atomic nucleus emits an alpha particle, and thereby transforms (or "decays") into an atom with a mass number decreased by 4 and atomic number decreased by 2.

3.
Taking an X-ray image with early Crookes tube apparatus in 1896. The Crookes tube is visible in the centre. The standing man is viewing his hand with a fluoroscope screen; this was a common way of setting up the tube. No precautions against radiation exposure are being taken; its hazards were not known at the time.

4.
Gamma-ray energy spectrum of uranium ore (inset). Gamma-rays are emitted by decaying nuclides, and the gamma-ray energy can be used to characterize the decay (which nuclide is decaying to which). Here, using the gamma-ray spectrum, several nuclides that are typical of the decay chain of 238 U have been identified: 226 Ra, 214 Pb, 214 Bi.

Natural abundance
–
In physics, natural abundance refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass of these isotopes is the weight listed for the element in the periodic table. The abundance of an isotope varies from planet to planet, and even place to place on the Earth. As an example, uranium has thre

1.
Contents

Half-life
–
Half-life is the time required for a quantity to reduce to half its initial value. The term is used in nuclear physics to describe how quickly unstable atoms undergo. The term is used more generally to characterize any type of exponential or non-exponential decay. For example, the medical sciences refer to the biological half-life of drugs, the con

1.
Half life demonstrated using dice in a classroom experiment

Decay product
–
In nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps, 234Th is the daughter of the parent 238U. 234mPa is the granddaughter of 238U and these might also be referred to as the daughter products of 238U. Decay products are important in understanding rad

1.
The decay chain from lead-212 down to lead-208, showing the intermediate decay products.

Stable isotope
–
The term stable isotope has a similar meaning to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element, the relative abundance of such stable isotopes can be measured experimentally, yielding an isotope ratio that can be used as a

1.
Nuclear physics

Beta emission
–
In nuclear physics, beta decay is a type of radioactive decay in which a beta ray, and a neutrino are emitted from an atomic nucleus. Neither the beta particle nor its associated neutrino exist within the prior to beta decay. By this process, unstable atoms obtain a more stable ratio of protons to neutrons, the probability of a nuclide decaying due

1.
A beta spectrum, showing a typical division of energy between electron and antineutrino

2.
β − decay in an atomic nucleus (the accompanying antineutrino is omitted). The inset shows beta decay of a free neutron. In both processes, the intermediate emission of a virtual W− boson (which then decays to electron and antineutrino) is not shown.

Standard atomic weight
–
The standard atomic weight is a physical quantity for a chemical element, expressed as relative atomic mass. It is specified by the IUPAC definition of natural, stable, because of this practical definition, the value is widely used as the atomic weight for real life substances. For example, in pharmaceuticals and scientific research, out of 118 che

1.
The atomic number of hydrogen is 1. The standard atomic weight of hydrogen is 1.008 (this value is not given here as an expectation interval, as it is in elements below). Atomic weight is the same as relative atomic mass. The atomic weights of samples of hydrogen will vary according to their content of heavy hydrogen (deuterium), and this will in turn depend upon where the samples are collected.

Tin
–
Tin is a chemical element with symbol Sn and atomic number 50. It is a metal in group 14 of the periodic table. It is obtained chiefly from the mineral cassiterite, which contains tin dioxide, Tin shows a chemical similarity to both of its neighbors in group 14, germanium and lead, and has two main oxidation states, +2 and the slightly more stable

List of elements by stability of isotopes
–
This is a list of the chemical elements and their isotopes, listed in terms of stability. Atomic nuclei consist of protons and neutrons, which each other through the nuclear force. These two forces compete, leading to some combinations of neutrons and protons being more stable than others, neutrons stabilize the nucleus, because they attract proton

1.
Isotope half-lives. Note that the darker more stable isotope region departs from the line of protons (Z) = neutrons (N), as the element number Z becomes larger

Magic number (physics)
–
In nuclear physics, a magic number is a number of nucleons such that they are arranged into complete shells within the atomic nucleus. The seven most widely recognized magic numbers as of 2007 are 2,8,20,28,50,82, large isotopes with magic numbers of nucleons are said to exist in an island of stability. Unlike the magic numbers 2–126, which are rea

1.
Graph of isotope stability.

Fission product yield
–
Nuclear fission splits a heavy nucleus such as uranium or plutonium into two lighter nuclei, which are called fission products. Yield refers to the fraction of a product produced per fission. Yield can be broken down by, Individual isotope Chemical element spanning several isotopes of different mass number, nuclei of a given mass number regardless

Nuclear waste
–
Radioactive waste is waste that contains radioactive material. Radioactive waste is usually a by-product of nuclear generation and other applications of nuclear fission or nuclear technology, such as research. Radioactive waste is hazardous to most forms of life and the environment, and is regulated by government agencies in order to protect human

1.
Activity of U-233 for three fuel types

2.
Total activity for three fuel types

3.
Removal of very low-level waste

4.
Spent fuel flasks are transported by railway in the United Kingdom. Each flask is constructed of 14 in (360 mm) thick solid steel and weighs in excess of 50 tons

Actinides
–
The actinide /ˈæktᵻnaɪd/ or actinoid /ˈæktᵻnɔɪd/ series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, the informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinid

3.
Glenn T. Seaborg and his group at the University of California at Berkeley synthesized Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No and element 106, which was later named seaborgium in his honor while he was still living. They also synthesized more than 100 atomic actinide isotopes.

4.
Unprocessed uranium ore

Nuclear fission
–
In nuclear physics and nuclear chemistry, nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts. The fission process often produces free neutrons and gamma photons, Frisch named the process by analogy with biological fission of living cells. It is a reaction which can r

1.
The mushroom cloud produced by Tsar Bomba, currently the largest man-made nuclear device detonated in history, next to other mushroom clouds of various nuclear devices.

3.
The cooling towers of the Philippsburg Nuclear Power Plant, in Germany.

Thermal neutron
–
The neutron detection temperature, also called the neutron energy, indicates a free neutrons kinetic energy, usually given in electron volts. The term temperature is used, since hot, thermal and cold neutrons are moderated in a medium with a certain temperature, the neutron energy distribution is then adopted to the Maxwellian distribution known fo

1.
Science with Neutrons

Fast neutron
–
The neutron detection temperature, also called the neutron energy, indicates a free neutrons kinetic energy, usually given in electron volts. The term temperature is used, since hot, thermal and cold neutrons are moderated in a medium with a certain temperature, the neutron energy distribution is then adopted to the Maxwellian distribution known fo

1.
Science with Neutrons

Fusion neutron
–
The neutron is a subatomic particle, symbol n or n0, with no net electric charge and a mass slightly larger than that of a proton. Protons and neutrons, each with approximately one atomic mass unit, constitute the nucleus of an atom. Their properties and interactions are described by nuclear physics, the nucleus consists of Z protons, where Z is ca

1.
Institut Laue–Langevin (ILL) in Grenoble, France – a major neutron research facility.

2.
The quark structure of the neutron. The color assignment of individual quarks is arbitrary, but all three colors must be present. Forces between quarks are mediated by gluons.

3.
Cold neutron source providing neutrons at about the temperature of liquid hydrogen

Fissile
–
In nuclear engineering, fissile material is material capable of sustaining a nuclear fission chain reaction. By definition, fissile material can sustain a reaction with neutrons of any energy. The predominant neutron energy may be typified by slow neutrons or fast neutrons. Fissile material can be used to fuel thermal-neutron reactors, fast-neutron

Uranium-233
–
Uranium-233 is a fissile isotope of uranium that is bred from thorium-232 as part of the thorium fuel cycle. Uranium-233 was investigated for use in weapons and as a reactor fuel. It has been used successfully in experimental nuclear reactors and has proposed for much wider use as a nuclear fuel. It has a half-life of 160,000 years, uranium-233 is

1.
Molten-Salt Reactor Experiment

2.
Shippingport Atomic Power Station

3.
German THTR-300

4.
The first detonation of a nuclear bomb that included U-233, on 15 April 1955.

Uranium-235
–
Uranium-235 is an isotope of uranium making up about 0. 72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i. e. it can sustain a chain reaction. It is the fissile isotope that is a primordial nuclide or found in significant quantity in nature. Uranium-235 has a half-life of 703.8 million years and it was discovered

1.
Full table

Uranium-238
–
Uranium-238 is the most common isotope of uranium found in nature, making up over 99% of it. Unlike uranium-235 it is non-fissile, which means it cannot sustain a chain reaction, however, it is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239. 238U cannot support a chain reaction because inelastic

1.
Full table

Plutonium-239
–
Plutonium-239 is an isotope of plutonium. Plutonium-239 is the fissile isotope used for the production of nuclear weapons. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in thermal spectrum reactors, along with uranium-235. Plutonium-239 has a half-life of 24,110 years, plutonium-239 can also absorb neutrons and fi

1.
Full table

Plutonium-241
–
Plutonium-241 is an isotope of plutonium formed when plutonium-240 captures a neutron. Like Pu-239 but unlike 240Pu, 241Pu is fissile, with a neutron cross section about 1/3 greater than 239Pu. In the non-fission case, neutron capture produces plutonium-242, in general, isotopes with an odd number of neutrons are both more likely to absorb a neutro

1.
Full table

Radioisotope
–
A radionuclide is an atom that has excess nuclear energy, making it unstable. During those processes, the radionuclide is said to undergo radioactive decay, the unstable nucleus is more stable following the emission, but will sometimes undergo further decay. Radioactive decay is a process at the level of single atoms. However, for a collection of a

1.
Americium-241 container in a smoke detector.

2.
Americium-241 capsule as found in smoke detector. The circle of darker metal in the center is americium-241; the surrounding casing is aluminium.

Halflife
–
Half-life is the time required for a quantity to reduce to half its initial value. The term is used in nuclear physics to describe how quickly unstable atoms undergo. The term is used more generally to characterize any type of exponential or non-exponential decay. For example, the medical sciences refer to the biological half-life of drugs, the con

1.
Half life demonstrated using dice in a classroom experiment

2.
Simulation of many identical atoms undergoing radioactive decay, starting with either 4 atoms per box (left) or 400 (right). The number at the top is how many half-lives have elapsed. Note the consequence of the law of large numbers: with more atoms, the overall decay is more regular and more predictable.

Gamma radiation
–
Gamma ray, denoted by the lower-case Greek letter gamma, is penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei. It consists of photons in the highest observed range of photon energy, paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by r

2.
Illustration of an emission of a gamma ray (γ) from an atomic nucleus

4.
A hypernova. Artist's illustration showing the life of a massive star as nuclear fusion converts lighter elements into heavier ones. When fusion no longer generates enough pressure to counteract gravity, the star rapidly collapses to form a black hole. Theoretically, energy may be released during the collapse along the axis of rotation to form a long duration gamma-ray burst.

Nuclear power plant
–
A nuclear power plant or nuclear power station is a thermal power station in which the heat source is a nuclear reactor. As is typical in all conventional thermal power stations the heat is used to steam which drives a steam turbine connected to an electric generator which produces electricity. As of 23 April 2014, the IAEA report there are 449 nuc

1.
A nuclear power station (Grafenrheinfeld Nuclear Power Plant, Grafenrheinfeld, Bavaria, Germany). The nuclear reactor is contained inside the spherical containment building in the center - left and right are cooling towers which are common cooling devices used in all thermal power stations, and likewise, emit water vapor from the non- radioactive steam turbine section of the power plant.

2.
Nuclear power plant in Jaslovské Bohunice in Slovakia.

3.
The control room at an American nuclear power plant.

4.
The Bruce Nuclear Generating Station, the largest nuclear power facility in the world

Slow neutron
–
The neutron detection temperature, also called the neutron energy, indicates a free neutrons kinetic energy, usually given in electron volts. The term temperature is used, since hot, thermal and cold neutrons are moderated in a medium with a certain temperature, the neutron energy distribution is then adopted to the Maxwellian distribution known fo

1.
Science with Neutrons

Pu-239
–
Plutonium-239 is an isotope of plutonium. Plutonium-239 is the fissile isotope used for the production of nuclear weapons. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in thermal spectrum reactors, along with uranium-235. Plutonium-239 has a half-life of 24,110 years, plutonium-239 can also absorb neutrons and fi

1.
Full table

Fast reactor
–
A fast neutron reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons. Such a reactor needs no moderator, but must use fuel that is relatively rich in fissile material when compared to that required for a thermal reactor. In order to sustain a chain reaction, the neutrons

1.
Shevchenko BN350 desalination unit. View of the only nuclear-heated desalination unit in the world

2.
Shevchenko BN350 nuclear fast reactor and desalination plant situated on the shore of the Caspian Sea. The plant generated 135 MW e and provided steam for an associated desalination plant. View of the interior of the reactor hall.

Nuclear weapon
–
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from small amounts of matter. The first test of a bomb released the same amount of energy as approximately 20,000 tons of TNT. The first thermonucl

1.
The mushroom cloud of the atomic bombing of the Japanese city of Nagasaki on August 9, 1945 rose some 11 miles (18 km) above the bomb's hypocenter.

2.
Nuclear weapons

3.
Edward Teller, often referred to as the "father of the hydrogen bomb"

4.
A demilitarized and commercial launch of the Russian Strategic Rocket Forces R-36 ICBM; also known by the NATO reporting name: SS-18 Satan. Upon its first fielding in the late 1960s, the SS-18 remains the single highest throw weight missile delivery system ever built.

Minor actinides
–
The minor actinides are the actinide elements in used nuclear fuel other than uranium and plutonium, which are termed the major actinides. The minor actinides include neptunium, americium, curium, berkelium, californium, einsteinium, the most important isotopes in spent nuclear fuel are neptunium-237, americium-241, americium-243, curium-242 throug

Californium
–
Californium is a radioactive metallic chemical element with symbol Cf and atomic number 98. The element was first made in 1950 at the University of California Radiation Laboratory in Berkeley, the element was named after the university and the state of California. Two crystalline forms exist for californium under normal pressure, one above, a third

1.
Californium, 98 Cf

2.
The 60-inch-diameter (1.52 m) cyclotron used to first synthesize californium

3.
Fifty-ton shipping cask built at Oak Ridge National Laboratory which can transport up to 1 gram of 252 Cf. Large and heavily shielded transport containers are needed to prevent the release of highly radioactive material in case of normal and hypothetical accidents.

Proton
–
A proton is a subatomic particle, symbol p or p+, with a positive electric charge of +1e elementary charge and mass slightly less than that of a neutron. Protons and neutrons, each with masses of one atomic mass unit, are collectively referred to as nucleons. One or more protons are present in the nucleus of every atom, the number of protons in the

1.
Ernest Rutherford at the first Solvay Conference, 1911

2.
The quark structure of the proton. The color assignment of individual quarks is arbitrary, but all three colors must be present. Forces between quarks are mediated by gluons.

Neutron
–
The neutron is a subatomic particle, symbol n or n0, with no net electric charge and a mass slightly larger than that of a proton. Protons and neutrons, each with approximately one atomic mass unit, constitute the nucleus of an atom. Their properties and interactions are described by nuclear physics, the nucleus consists of Z protons, where Z is ca

1.
Institut Laue–Langevin (ILL) in Grenoble, France – a major neutron research facility.

2.
The quark structure of the neutron. The color assignment of individual quarks is arbitrary, but all three colors must be present. Forces between quarks are mediated by gluons.

3.
Cold neutron source providing neutrons at about the temperature of liquid hydrogen

Beta decay
–
In nuclear physics, beta decay is a type of radioactive decay in which a beta ray, and a neutrino are emitted from an atomic nucleus. Neither the beta particle nor its associated neutrino exist within the prior to beta decay. By this process, unstable atoms obtain a more stable ratio of protons to neutrons, the probability of a nuclide decaying due

1.
A beta spectrum, showing a typical division of energy between electron and antineutrino

2.
β − decay in an atomic nucleus (the accompanying antineutrino is omitted). The inset shows beta decay of a free neutron. In both processes, the intermediate emission of a virtual W− boson (which then decays to electron and antineutrino) is not shown.

Proton emission
–
Proton emission is a rare type of radioactive decay in which a proton is ejected from a nucleus. For a proton to escape a nucleus, the proton separation energy must be negative - the proton is therefore unbound, Proton emission is not seen in naturally occurring isotopes, proton emitters can be produced via nuclear reactions, usually using linear p

2.
The decay of a proton rich nucleus A populates excited states of a daughter nucleus B by β+ emission or electron capture (EC). Those excited states that lie below the separation energy for protons (Sp) decay by γ emission towards the groundstate of daughter B. For the higher excited states a competitive decay channel of proton emission to the granddaughter C exists, called β-delayed proton emission.

Electron capture
–
Electron capture is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shell. This process thereby changes a proton to a neutron and simultaneously causes the emission of an electron neutrino. P + e− → n + ν e The daughter nuclide, if it is in an excited stat

Observationally Stable
–
Stable nuclides are nuclides that are not radioactive and so do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, the 80 elements with one or more stable isotopes comprise a total of 254 nuclides that have not been known to decay using current equipment. Of these elements,26 have only

1.
Graph of nuclides (isotopes) by type of decay. Orange and blue nuclides are unstable, with the black squares between these regions representing stable nuclides. The unbroken line passing below many of the nuclides represents the theoretical position on the graph of nuclides for which proton number is the same as neutron number. The graph shows that elements with more than 20 protons must have more neutrons than protons in order to be stable.